Technical Abstract:
Purple and yellow nutsedges (Cyperus rotundus and C. esculentus) are the most troublesome weeds in the cropping systems in Florida and the Caribbean where they have been reported to cause yield losses of 20-89% in different horticultural crops. Production systems based on plastic mulching and methyl bromide soil fumigation are used for nutsedge suppression in many conventional vegetable cropping systems. When methyl bromide is phased out, the losses due to nutsedges are expected to increase in conventional horticultural crops. Organic production will continue to suffer due to a lack of effective weed control measures. As an alternative to the plastic mulch-methyl bromide system, 10 organic hays (shoot straw of bahiagrass, cogongrass, cowpea, millet, nutsedge, sorghum Sudangrass, sunnhemp, rye, corn, and sugarcane bagasse), four green mulches (cowpea, millet, sorghum Sudangrass, and sunnhemp), and two plastic mulches (black and IRT) were tested for their efficacy in suppressing purple and yellow nutsedge growth in a raised bed tomato (cv. Tygress) field. The beds were fumigated with methyl bromide prior to treatment establishment and a randomized complete block design was used with four replications. Tomato seedlings were transplanted in a single row in all plots at a rate of six tomato seedlings per plot with 18” plant spacing. The following day, nutsedge tubers were seeded, with yellow and purple nutsedge tubers seeded alternately at 1' depth and 3' space in two lines parallel to tomato rows (one line on each side with 2' spacing from tomatoes). Only the plot of weed-free control treatment in each block was not seeded with nutsedge. After seeding the nutsedge tubers, the hays and green or plastic mulches were spread in each plot. The black plastic mulch consistently reduced nutsedge emergence and growth more than the organic mulches and the IRT plastic mulch. All green organic mulches, except the green sunnhemp, were more suppressive to nutsedge emergence and growth than hay mulches. Among the organic mulches, the best suppressive effect on nutsedge was found when using green sorghum, green millet, and congongrass hay followed by green cowpea and bahiagrass hay. Sugarcane bagasse, corn hay, green sunnhemp, and yellow nutsedge hay provided the least nutsedge suppression. Thus, some of the organic mulches may be used to reduce purple and yellow nutsedge populations in tomato production in Florida.